Efeito do uso e da granulometria do carbureto de cálcio no refino secundário de aços

Abstract

For the past decades decades, the use of calcium carbide as a reducing agent in secondary steelmaking was extensively covered by many studies studies. The main characteristics sought in this material, among many others, are its effect on reducing the oxidation of steel and slag in the ladle, greater efficiency in desulfurization, reduction of silicon and manganese losses to the slag and control the number of inclusions non-metallic present in the semi-finished product. In order to get the most out of the benefits of using this material, several methodologies have been tested during the steelmaking. The way that presents the most results in its use is the addition during the tapping of steel from the Electric Arc Furnace (EAF) to the ladle. Aspects such as amount added, granulometry and the combined use with other deoxidizers must be considered for each place where the carbide will be inserted. Not considering these aspects may result in inefficiency in the use of the material or offer a risk situation for the operation. Because to the criticality in the addition of calcium carbide during tapping, it is necessary to structure a methodology for carrying out the tests. During this work, aspects related to the choice of granulometry were emphasized, which is a feature not yet appreciated by previous studies. Through the development of the methodology, it was possible to determine the added amount of 20kg for the conditions observed in the process, being necessary to carry out the restriction of dissolved oxygen in the evaluated heats. Two granulometries were used, one varying between 0 and 4 millimeters (mm) and the other between 2 and 10 millimeters (mm). Improvements in deoxidation, desulfurization and alloy yield were observed for most of the tests using the two carbide granulometries, with emphasis on the 0 to 4 mm granulometry, which showed more promising results, however, as it presents similar results and does not present a more active reaction in the first moments of leakage, a granulometry of 2 to 10 mm is considered more suitable for use.